(1) Field of the Invention
The present invention relates to a waterproof structure of an electric junction box, in which a grommet for waterproof is mounted thereon to guide a wiring harness out from the junction box, thereby preventing water from entering into the junction box.
(2) Description of the Related Art
FIG. 11 illustrates a typical example of a conventional waterproof structure of an electric junction box.
The electric junction box (hereinafter, junction box) includes a case 71 made of synthetic resin, a cover 72 made of synthetic resin, a junction unit (not shown) including a fuse, relay and so on, which is received in the case 71, and a resilient grommet 73 for waterproof. A U-shaped notch 74 for guiding out a wiring harness is formed on one side wall of the case 71 and a guide member 75 is formed projectingly outward from the periphery of the notch 74. The grommet 73 slidingly fits into the guide member 75 so that the wiring harness (a plurality of wires) 76 continuing to the junction unit (not shown) is inserted through the grommet 73 and guided out therefrom.
The grommet 73 includes a bellows 77, a cylinder 78 having small diameter continuing to one end of the bellows 77, a flange 79 continuing to the other end of the bellows 77, and a reinforcing member (not shown) made of synthetic resin fit into the flange 79. The flange 79 slidingly fits into the guide member 75 of the case 71 and the cover 72 covers the case 71 so as to make the upper surface of the flange 79 adhere to the lower surface of the cover 72, thereby preventing water from entering into the case 71 from the outer periphery of the flange 79.
A rectangular annulus packing (not shown) is provided on the inner periphery of the cover 72 and the upper edge of the case 71 adheres to the packing, thereby preventing water from entering from the junction between the case 71 and cover 72. The end of the cylinder 78 of the grommet 73 is wound with a vinyl tape (not shown) after the wiring harness 76 is inserted through the grommet 73, thereby preventing water from entering.
However, in the conventional waterproof structure of a junction box, for example in a case of truck, in which the junction box is mounted thereon being exposed to outside, when rainwater leaped up during traveling, water during vehicle washing or high-pressure water during vehicle washing with the high-pressure water directly hits the flange 79 of the grommet 73, the water enters between the flange 79 and case 71 or cover 72, thereby causing a problem. In the event that water enters into the case 71, the water possibly adversely affects the junction unit and so on in the case 71.
On the other hand, in Japanese Patent Publication No. H8-288667 (not shown in the figure) described is a structure, in which the case is formed with double walls and each wall fits into the flange of the waterproof grommet. However, in this case, the waterproof structure becomes large in size and the structure of the grommet becomes complicated, thereby causing another problem.
It is therefore an objective of the present invention to solve the above problems and to provide a waterproof structure of an electric junction box, by which rainwater, water during vehicle washing or high-pressure water during vehicle washing with the high-pressure water, which strongly hits the grommet, does not enter into the case and the waterproof structure can be minimized and simplified.
In order to attain the above objective, the present invention is to provide a waterproof structure of an electric junction box comprising:
a case including a notch and a guide member formed along the periphery of the notch;
a resilient grommet for inserting a wiring harness therethrough including a flange which fits into the guide member; and
a cover for covering the case from above the flange, wherein the flange includes at least two flange parts formed integrally with each other, a height and width of the first flange part situated relatively farther from the case being formed smaller than those of the second flange part situated relatively nearer to the case, respectively.
With the construction described above, even when water leaped up during traveling or high-pressure water during vehicle washing strongly hits the flange of the grommet and passes through the adherent portion of the first flange part, the first flange part weakens the water energy and the second flange part securely waterproofs the junction box.
Further, since the first and second flange parts are integrally formed with each other, the waterproof structure according to the present invention is simplified and minimized compared to a conventional grommet having double flanges fitting into double walls of a junction box body, thereby the junction box can be minimized.
Preferably, the case is provided with first and second guide walls fitting with the first and second flange parts, respectively, as the guide member.
With the construction described above, since each flange part is held by the corresponding guide wall, even when high-pressure water hits and bends the first flange part, the second flange part securely waterproofs the junction box without being affected by the water. Therefore, the waterproof performance is significantly improved.
Preferably, each top of the first and second flange parts projects higher than the guide member so that both said tops adhere to the cover.
With the construction described above, since the top of each flange part resiliently abuts against the cover, the top of the second flange part securely waterproofs the junction box even when water passes over the top of the first flange part.
Preferably, the top of the first flange part adheres to an inner surface of the cover while the top of the second flange part adheres to a packing in the cover.
With the construction described above, the first flange part directly adheres to the inner surface of the cover and resists against the high-pressure water with the strong adhering force. The second flange part resists against the water, the energy of which has been weakened, and waterproofs the junction box with the contact with the packing.
Thus, with the two-step shielding against water, the water is securely prevented from entering from between the flange and cover.
Preferably, a peripheral wall of the case is formed doubly inner and outer, the inner peripheral wall is formed higher than the outer peripheral wall, and the height of the first guide wall is set equal to that of the outer peripheral wall while the height of the second guide wall is set equal to that of the inner peripheral wall.
With the construction described above, even when water hits the outer peripheral wall and enters into the inside, the water is stopped by the high inner peripheral wall and prevented from entering into the inside of the inner peripheral wall. Further, the water which enters into the inside of the first guide wall hits the high second guide wall and thereby is prevented from entering further. Therefore, the cooperative action between each guide wall and the flange of the grommet significantly improves the waterproof performance.
Preferably, the bottom of the first guide wall is provided with a hole for draining water.
With the construction described above, water which enters inside the first guide wall is drained through the hole at the bottom, thereby the water pressure (i.e. water energy) which applies to the second flange part inside the second guide wall is reduced. Therefore, the second flange part securely waterproofs the junction box.
Preferably, the grommet is provided with a third flange part adjacently to the second flange part and the cover is provided with a third guide wall fitting with the third flange part.
With the construction described above, since the third flange part adheres to the third guide wall, the third flange part securely stops water in the event that the water passes through the second flange part. Further, the third flange part reinforces the second flange part so as to improve the waterproof performance of the second flange part. Therefore, the waterproof performance is significantly improved.
Preferably, the top of the third flange part adheres to the packing.
With the construction described above, the cooperative action between the top of the third flange part and the top of the second flange part securely prevents the water which passes through the first flange part from entering. Therefore, the waterproof performance is significantly improved.
Preferably, a reinforcing member is mounted in the flange and locked to the case by locking means.
With the construction described above, the flange is fixed to the case integrally with the reinforcing member, thereby -preventing the flange from coming out or from shifting in the guide member. Therefore, the waterproof performance is significantly improved.